> What would be the benefit of having a browser with a new web engine?

This is the right question. The answer is probably what you're thinking: Absolutely nothing. It'd be a giant waste of time to spend 5 years rebuilding plumbing instead of focusing on where one can actually differentiate.

5? more like 10. Servo was in development for 8 years before Mozilla pulled the plug and it was nowhere near production ready. And the people working on it were experienced browser engineers already.

> What would be the benefit of having a browser with a new web engine?

It would be beneficial if it can be more easily modified and customized and the pieces can be taken apart and used independently or combined differently. Furthermore, some parts might be able to be made more efficient in some ways.

And then, actual progress and actual improvements can be made; to be improved would mean some things might need deliberately differently, etc. This way it can be one design mainly or only for advanced users who are assumed to know what they are doing, etc.

What would be the benefit of having more than one word processor, compiler, database, operating system or photo manipulation system?

I say competition and innovation as well as selection. For browsers security. How can I mmention security?

Well, if Chromium has a serious bug, it impacts millions and millions.

Having different engines should hopefully mean some are immune to that particular one so you cant win the grand prize with a hack for one engine.

Competition and funding for non chromium initiatives.

If someoone had asked the same question before chrome would you have agreed with them?

Well, Google didn’t develop a new engine for Chrome. They forked WebKit. And then Samsung, Microsoft, and others forked Chromium for their own browsers. (These forks are kept close to Chromium, but they’re still forks.)